#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 1024
void error_handling(char *message);

int main(int argc, char *argv[])
{
    int recv_sock;
    struct sockaddr_in addr;
    int str_len;
    char buf[BUF_SIZE];

    if(argc!=2) {
        printf("Usage : %s  <PORT>\n", argv[0]);
        exit(1);
    }

    recv_sock=socket(PF_INET, SOCK_DGRAM, 0);

    memset(&addr, 0, sizeof(addr));
    addr.sin_family=AF_INET;
    addr.sin_addr.s_addr=htonl(INADDR_ANY);	
    addr.sin_port=htons(atoi(argv[1]));

    if(bind(recv_sock, (struct sockaddr*)&addr, sizeof(addr))==-1)
        error_handling("bind() error");

    while(1)
    {
        str_len=recvfrom(recv_sock, buf, BUF_SIZE-1, 0, NULL, 0);
        if(str_len<0) 
            break;
        buf[str_len]=0;
        fputs(buf, stdout);
        fflush(stdout);
    }

    close(recv_sock);
    return 0;
}

void error_handling(char *message)
{
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}
